Until now there is a lack of objective methods to evaluate the clinical efficacy of low level lasers (LLL). The reported results in this paper are showing that the cutaneous ultrasound could be a valuable method to be used in order to objectify the results obtained in low level laser therapy (LLLT). 52 patients with osteoarthritis were divided into three groups: Group A:19 patients treated with IR emitted laser diode, CW, 3mW power, 780 nm wavelengths. Group B: 18 patients treated with the same IR laser diode as above and He-Ne laser, CW, 2mW power. Group C: 14 patients exposed to placebo laser. To every patient was done cutaneous ultrasound before and after LLLT and we followed also the clinical evolution. The positive results meaning significant US favorable changes were found in 73.9 percent for group A and 77.7 percent for group B and 21.4 percent for PLACEBO group. We conclude that cutaneous ultrasound could be an objective method to appreciate the clinical efficacy of low power lasers.